1. Field of the Invention
The present invention relates generally to arc furnaces and more particularly to an improved sturcture for moving the roof thereof during charging operations.
2. Description of the Prior Art
The generally accepted method of operating arc furnaces today is to charge the furnaces by means of so-called charging buckets. For this purpose, all the furnace components above the furnace shell, i.e. the roof and superstructure, have to be brought temporarily to the side so that the charging bucket can be moved over the furance and emptied thereinto.
Various constructions have heretofore been used to achieve this purpose. With one of these, the furnace superstructure, with the furnace roof suspended therefrom, can be swivelled about a round column standing next to the furnace shell. A configuration of this kind is illustrated on page 3 of an undated brochure entitled "Massbild zu Lichtbogen-Schmelzofen, Typen SSKD 260-390" and published by BBC Brown Boveri & Company, Limited, Baden, Switzerland.
The arrangement described results in an eccentric bending load on the column and has to be dimensioned according to the maximum permissible bending stress and/or the deflection that must not be exceeded. Even with medium-sized furnaces, both these criteria give rise to steel forgings or castings which are of substantial size and relatively expensive. Hollow steel castings are also expensive. Endeavors to perform the roof swivelling function in another way not requiring a rotating column, however, do not lead to space-saving constructions such as are offered by the rotating column. The problem is therefore to find a less expensive solution for the rotating column.